Does a rear extension always count as permitted development?

Only if it stays within the GPDO Class A limits for depth, height and boundary distance, the property isn't in an area with an Article 4 direction removing those rights, and less than 50% of the curtilage is already covered by extensions or outbuildings.

What if my property is in a conservation area?

Conservation area status tightens several permitted development limits, particularly for side extensions and roof work facing a highway. Use the checker below with your postcode - it flags conservation areas automatically.

What if my extension goes beyond the Prior Approval depth limit?

Then it needs full planning permission — Prior Approval only extends the automatic permitted development depth, it doesn't remove the upper limit entirely.

Planning permission for a rear extension on a semi-detached house

Under GPDO 2015 Schedule 2, Class A, many rear extension projects on a semi-detached house qualify as permitted development if they stay within set limits. Enter your postcode and dimensions below for a verdict specific to your address.

Permitted Development & Cost Checker

England only. Takes about a minute.

Permitted development limits for a rear extension on a semi-detached house

Depth: Up to 3m without approval, or up to 6m via Prior Approval (neighbour consultation).
Height: Up to 4m overall.
Eaves height: Must not exceed 3m within 2m of a boundary.
Curtilage coverage: Buildings other than the original house must not cover more than 50% of the curtilage.

Article 4 directions and conservation areas can remove or tighten these rights locally — checked automatically above. Always confirm with a Lawful Development Certificate before starting work.

Cost of a rear extension by region

London South East East of England South West West Midlands East Midlands North West Yorkshire and the Humber North East

Planning fees by council

Fees and decision times for a rear extension vary by council. Find yours below.

London

South East

East of England

South West

West Midlands

East Midlands

North West

Yorkshire and the Humber

Leeds Sheffield York Bradford Kingston upon Hull Wakefield Barnsley Calderdale Doncaster East Riding of Yorkshire Kirklees North East Lincolnshire North Lincolnshire North Yorkshire Rotherham

North East

Newcastle upon Tyne Sunderland Middlesbrough Gateshead County Durham Darlington Hartlepool North Tyneside Northumberland Redcar and Cleveland South Tyneside Stockton-on-Tees

Rules version 2026.1 · last reviewed 2026-01-01